Scalable video coding (SVC) provides three scalability functions. First, a resolution scalability (or spatial scalability) function is provided to restore a part of received data to a video signal with a different resolution according to changes in channel capacity. Second, a frame scalability (or temporal scalability) function is provided to restore the received data to a video signal having various frame-rates. Last, a signal to noise ratio (SNR) scalability function is provided to reproduce a signal of a different video quality by decoding only part of the signal when information is partially received due to channel capacity constraints.
Various effective methods have been proposed in order to enhance capability of the SVC codec having the aforementioned features. Examples of the methods include a variable group of pictures (GOP) technique, an effective motion estimation technique, an optimized quantization technique, and so on. One of the most important techniques is a bit allocation technique that allocates bits for respective coding components.
This is because the bit allocation technique determines a video quality and has an effect on other modules of the codec (for example, motion estimation, quantization, etc). Therefore, the effective bit allocation technique for SVC has to be developed in order to improve capability of the SVC codec.
However, the method of controlling a bit-rate by using the conventional SVC codec has a problem in that an optimal video quality cannot be obtained at any bit-rate since not only initial quantization parameter (QP) values have to be properly known for all images but also the QP values are used in units of frames.
In addition, in the conventional technique, a high quality image can be obtained only when the suitable initial QP values are known for all sequences. However, if the initial QP values of an image are unknown, various problems occur. For example, when an image having a lot of motion is coded by using a large QP value, a low quality image may be produced. Furthermore, when an image having less motion is coded by using a small QP value, a large amount of bits are generated.